Electrified Railway Research Articles

Intelligent cotter pins defect detection for electrified railway based on improved faster R-CNN and dilated convolution

The cotter pin (CP) is a vital fastener for the catenary support components (CSCs) of high-speed electrified railways. Due to the vibration and excitation caused by the passing of railway vehicles, some CPs may be broken or fallen off over time, which poses a significant safety hazard to the railway systems. Currently, the CP defect detection is primarily conducted by humans, which is inefficient and inconsistent. Therefore, there is an urgent need for automatic CP defect detection to ensure railway safety. However, this task is very challenging as it requires covering hundreds or thousands of miles in limited times when the railway stops running. To this end, we first design a traffic track intelligent imaging device to capture catenary images at various angles at high speed. Then, inspired by the success of deep learning-based object detection, we develop a CP detection model based on an improved Faster R-CNN with a multi-scale region proposal network (MS-RPN) and propose the positive sample adaptive loss function (PSALF) to enhance detection accuracy. Finally, we propose a module to recognize the CP defect based on dilated convolution. The experimental results show that our method can effectively detect the CP defect in the catenary image, achieving 99.05 % precision and 98.40 % recall rate on CP defect detection. Furthermore, CP detection method and CP defect detection are significantly faster than baseline method, with FPS improvements of 2.76 and 24.67, respectively, thus making it more suitable for real-time applications in railway systems.

A Review on Single Phase AC System of Railway Electrification

The widespread adoption of 25 kV, 50 Hz single-phase AC supply in long-distance electrified railway systems poses significant challenges to power quality in transmission networks. This paper presents an in-depth investigation into the influence of electric railway systems on a 110 kV transmission system, with a specific focus on locomotives equipped with diode rectifiers. Harmonic currents generated by these locomotives and unbalanced voltages introduced by single-phase traction loads are known to adversely affect power system components, leading to issues such as overheating, additional losses, and interference with communication systems. The focus of this paper is not only to understand the fundamental principles but to conduct a deep exploration of the functioning of various components such as locomotives, contact lines, and substations. High voltage This voltage is supplied from the substation or directly from the generating station. This high AC voltage (25KV) is first transformed into low AC voltage (415V). Three-phase induction motors are used because they provide high torque, are reliable, and are more efficient. The AC voltage in the second phase is rectified to DC and then converted into a phase AC using VFD. The VFD provides variable frequency and voltage to run the induction motor at different speeds.

Fault-Tolerant Method of Modular Railway Power Conditioner Based on DC Bus Voltage Regulation

With the development of high-speed electrified railway, many serious power quality problems have arisen and caused widespread concern. In order to achieve comprehensive management of power quality, modular railway power conditioner (MRPC) has been applied to traction systems. However, due to the presence of multiple sub-modules (SMs). The reliability of the equipment is threatened as the number of SMs increases. In medium-voltage applications, system reliability can be improved by adding redundant SMs. However, when the redundant SMs are run out, the reliability of the whole system cannot be guaranteed. Therefore, a fault-tolerant method based on DC bus voltage regulation is proposed to improve the reliability of MRPC by modulation signal reconstruction. The proposed method not only achieves fault ride-through to maintain normal operation and improves the SMs voltage stress on the opposite converter, but also effectively improves the over-modulation. The effectiveness of the proposed method is verified by down-scale experiments.

Evaluation of Grid Support Capacity From Electrified Railways

High power level and temporal operation flexibility endow electric trains with great potential for improving grid resilience. It becomes crucial to quantify the grid support capacity (GSC) from large-scale electrified railways. This paper innovatively proposes a hierarchical train coordination and trajectory regulation method to evaluate and deliver the GSC from electrified railways. In the light of the mechanical energy consumption analysis of train running, the energy-oriented train operation model is proposed to avoid the nonlinear differential dynamics of train kinetics when coordinating large-scale trains. Then the aggregation and disaggregation of trains for grid support can be formulated as linear and convex quadratic programming problems respectively. To closely follow the reference power and enhance the feasibility of train operation, a novel iterative discretization approach is proposed to generate the precise reference trajectory. A sliding mode controller with disturbance bound adaption is devised to overcome the modeling errors and disturbances when deploying GSC in realistic environment. Comprehensive numerical examples verify the effectiveness of the proposed scheme, and demonstrate the significant grid support potential from collaborative electrified railways.

Research on Reliability Allocation Method for Traction Power Supply System of Electrified Railways in Mountainous Areas

Research on Reliability Allocation Method for Traction Power Supply System of Electrified Railways in Mountainous Areas

Optimal siting of substations of traction power supply systems considering seismic risk

The traction power supply system (TPSS) is a critical infrastructure that provides electrified railways with power. However, its safe and reliable operation is threatened by earthquake disasters. Due to the strong randomness, uneven spatial distribution, and destructive risk of earthquake disasters, it is crucial to develop reasonable planning schemes to mitigate seismic risks of the system. This paper proposes a substation optimal siting method considering seismic risks. By establishing the chain circuit model of the TPSS and employing the dynamic power flow calculation method, the power loss of the system is obtained. By integrating the earthquake scenario simulation and substation fragility analysis, the substation seismic risk is calculated through Monte Carlo simulation. On this basis, the optimization model for substation site selection is formulated, aiming to minimize both the system power loss and the substation seismic risk while adhering to constraints of construction cost, operating safety, and geographical locations. The Pareto optimal solutions are then obtained. Simulation analysis based on actual system parameters shows that compared with traditional site selection methods, the proposed method can effectively mitigate system seismic risks while considering system power loss, providing theoretical bases for the disaster prevention and mitigation in the TPSS planning.

A Novel Co-phase Traction Power Supply System in Electrified Railway

The electrified railway has power quality problems such as three phases seriously unbalanced, large harmonics, and reactive power. In addition, the neutral section exists at each power supply section, which restricts the development of the high-speed and heavy-haul railway. This paper proposes a novel co-phase traction power supply system (TPSS) based on a YNvd balanced transformer, which can not only solve the above problems but also save one single-phase coupling step-down transformer, thus reducing the cost and space of the whole system. In addition, the voltage level of the converter switching device can be reduced by the rational design of the transformer tap position, which enhances the reliability and feasibility of the system. The compensation principle and control strategy of the co-phase TPSS based on the novel YNvd balanced transformer are analyzed in detail in this paper, and the compensation current detection and integrated power flow controller (IPFC) control methods are given. Simulation and analysis show that the proposed topology structure and control method are correct and feasible.

EMI and IEMI Impacts on the Radio Communication Network of Electrified Railway Systems: A Critical Review

The electrified railway system has been rapidly rolled out in many countries and regions in the past decades, along with the transportation decarbonization agenda. The latest development in power electronics and electrical railway systems has increased the risks of electromagnetic interference (EMI) and intentional EMI (IEMI) emissions, introducing new challenges to the railway radio communications network. It is vital to have a robust and reliable railway communication network that can be resistant and immune to these interferences for the safe and efficient operation of modern railway systems. Yet, the source and new features of EMI and IEMI emerging along with the latest technological development have not been thoroughly investigated and understood. This review paper aims to fill the research gap. First, railway communications systems are introduced. The EMI and IEMI are discussed at the whole system level, and the corresponding impacts on the signaling and communication systems are reviewed comprehensively. Current electromagnetic compatibility (EMC) methods are surveyed, and challenges of tackling the impacts of EMI and IEMI on the signaling and communication systems are discussed. Finally, future research directions are outlined.

Hierarchical Energy Management of Networked Flexible Traction Substations for Efficient RBE and PV Energy Utilization Within ERs

The particular split-phase traction power system of AC electrified railways (ERs) restricts its regenerative braking energy (RBE) utilization and photovoltaic (PV) penetration. Networked flexible traction substation (FTSS) operation is a promising paradigm to address this restriction. Therefore, this paper proposes a networked FTSS system architecture that ties adjacent FTSSs via unified power flow controllers (UPFC) at sectioning posts (SPs), which matches the technical characteristics of split-phase ERs obtaining the lower capacity requirement. Correspondingly, a real-time hierarchical energy management strategy is designed. The networked FTSS management level optimizes the energy cooperation among FTSSs, i.e., the exchange power at SPs. It aims at maximizing the global RBE and PV energy utilization and shaving the maximum demand of each FTSS. At the individual FTSS management level, each FTSS autonomously regulates the power outputs of the local back-to-back converter and energy storage system to maximize the local RBE and PV energy utilization and improve the local power quality issues. These two energy management levels operate independently with different time scales, making the networked FTSS system have good extensibility and reliability. Finally, the performance of the proposed scheme is verified via hardware-in-the-loop tests.

A Comprehensive Review of Power Converters for E-Mobility

The penetration of electric vehicles is becoming more and more widespread and recently electric buses and trains are fetching the attention of researchers and developers. In this review, we examine the charging systems applied to the fast charging of electric vehicles and buses as well as the charging strategies, mainly applied to electric buses. We also briefly delve into power topologies for a more electrified railway system where we discuss their different supply systems as well as their motor drive systems. Problems and charge challenges for electric buses and trains are discussed too.

Painstaking Start of Railway Electrification in China: The Baocheng Electrified Railway(1952—1975)

Painstaking Start of Railway Electrification in China: The Baocheng Electrified Railway(1952—1975)

An Optimization Method for Maintenance Resource Allocation in Electrified Railway Catenary Systems

The traditional preventive maintenance plans of electrified railways are mainly formulated according to historical maintenance records and the experience of maintenance technicians. With the increase of the maintenance workload of catenary systems, traditional maintenance decision-making modes are hard to accommodate the demand for the high-efficiency and economical operation of catenary systems. To cater for the on-site maintenance demands, a conceptual framework towards the cost-effective optimization of catenary maintenance is proposed in this paper. The framework includes investigating and sorting the physical quantities in practical maintenance operations, modeling the maintenance operation process, establishing and solving the optimization model of the maintenance operator allocation with multiple optional objectives, and developing the human-machine application system, namely, the resource allocation system (RAS) with both hardware and software for electrified railway catenary maintenance. Field application shows that the implementation of RAS is superior to the current maintenance scheme in maintenance efficiency and cost, which can provide decision support for the scientific formulation of catenary system maintenance scheme, and promote the intelligent development of current maintenance modes.

Dynamic Voltage Unbalance Constrained Economic Dispatch for Electrified Railways Integrated Energy Storage

The cophase traction power supply system (CTPSS) is a promising solution in the smart electrified railways to effectively eliminate the neutral section, improve regeneration braking energy (RBE) utilization and mitigate voltage unbalance (VU). It works by coordinating the power flow distribution (PFD) among the energy storage (ES), power flow controller, and traction transformer. However, the conventional dispatch considering VU mitigation may result in increasing extra operation costs and accelerating ES aging. Therefore, driven by the day-ahead forecasted information, a dynamic VU regulation strategy is proposed to draw up the VU compensation schedule (VU-CS), which can satisfy the probabilistic limitations of power quality standards. Consequently, a Copula-based VU dependence model is developed to transform the VU-CS into the PFD constraint set of CTPSS. Meanwhile, an ES degradation model is introduced to quantify the system operation cost within different scenarios. Taking the PFD as a VU regulation constraint, an economic dispatch scheme of CTPSS is established to obtain a minimum operation cost and maximum RBE utilization. Finally, case study tests verify the efficiency of the proposed approach. The results show that scheme can improve ES cycle life and decrease cost under the probabilistic limitations of VU.

Improved fault location method for AT traction power network based on EMU load test

The autotransformer (AT) neutral current ratio method is widely used for fault location in the AT traction power network. With the development of high-speed electrified railways, a large number of data show that the relation between the AT neutral current ratio and the distance from the beginning of the fault AT section to the fault point (Q–L relation) is mostly nonlinear. Therefore, the linear Q–L relation in the traditional fault location method always leads to large errors. To solve this problem, a large number of load-related current data that can be used to describe the Q–L relation are obtained through the load test of the electric multiple unit (EMU). Thus, an improved fault location method based on the back propagation (BP) neural network is proposed in this paper. On this basis, a comparison between the improved method and the traditional method shows that the maximum absolute error and the average absolute error of the improved method are 0.651 km and 0.334 km lower than those of the traditional method, respectively, which demonstrates that the improved method can effectively eliminate the influence of nonlinear factors and greatly improve the accuracy of fault location for the AT traction power network. Finally, combined with a short-circuit test, the accuracy of the improved method is verified.

Exploration of the Development of New Technology of Electrified Railway Power Supply System

Exploration of the Development of New Technology of Electrified Railway Power Supply System

Study on the Modeling and Suppression of Arcing Generated by Articulated Split-Zone Insulator in Electrified Railways

In electrified railways, pantograph–catenary (PC) arc frequently occurs in the process of train passing through split-zone insulator, which threatens the current collection of PC and operation of electric multiple units (EMUs). So far, there have been a few studies on the analysis and modeling of the PC arc on split-zone insulator. It is noting that this research is different from that of split-phase region. This article first analyzes the dynamic variation process of PC distance as EMUs pass the insulator and deduces the formula, which can reflect the PC arc length variation according to the specific mechanical structure of insulator. Then, a black-box arc model of split-zone insulator is proposed. Next, a vehicle-to-grid model of the EMUs that contains the arc model of split-zone insulator is established to simulate and analyze the characteristics of the PC arc on split-zone insulator. Furthermore, the proposed arc model in this article is verified by comparing the simulated arc characteristic waveforms with the measured results. Finally, a sensitivity analysis of the arc model under different lifting angles of the contact wire is carried out in order to analyze the suppression of PC arc on split-zone insulator.

Review on Capacity Optimization of Traction Transformer for High-Speed Railway

In electrified railways, traction load not only fluctuates between peaks and valleys, but also has a situation of low utilization rate of average load throughout the day and short overload. The traction transformer selects the capacity with the peak load as the demand boundary, which will cause the capacity utilization rate to be low and even lead to the economic decline of the traction power supply system. This article summarizes the existing configuration methods for capacity optimization of traction transformer. Then under the conditions of energy storage and new energy access to traction power supply system, the three aspects are described as follows. Firstly, the energy storage device is connected to the system, which can pull the capacity of traction transformer to achieve peak shifting and valley filling. Then, the possibility of integrated configuration of new energy and traction power supply system to optimize the capacity of traction transformer and the methods of optimal configuration of traction transformer capacity by using new energy such as wind and light are summarized. Finally, this paper discusses the current structure of new energy access to traction power supply system, and it looks forward to the feasibility of new energy access to traction power supply system cooperating with energy storage devices to optimize the capacity of traction transformer.

Research on On-line Anti-icing Technology of Overhead Catenary of Electrified Railway

Research on On-line Anti-icing Technology of Overhead Catenary of Electrified Railway

Discussion on Key Points of OCS Construction Technology of Electrified Railway

Discussion on Key Points of OCS Construction Technology of Electrified Railway

Application of Satellite Remote Sensing Technology on Electrified Railway Network Greening Engineering

As the awareness of development of ecological civilization continues to strengthened, public expectations for landscape greening along the railway have gradually increased. The railway landscape greening has multiple functions of safety, environmental protection and aesthetics. Therefore, it is necessary to effectively combine the characteristics of the local area’s natural ecology, custom and culture. To reflect the corresponding key points in the landscape greening design process, and apply the scientific greening concept to the engineering design.